1. Field of the Invention
The field of the invention relates to data processing and in particular to the initialisation of a pipelined processor.
2. Description of the Prior Art
On switch on the state of some elements within a processor may need to be set to enable the processor to function as expected. For example, there may be certain behaviour that the programmers' model of the processor predicts will not happen unless certain values are stored in particular registers at start up. Thus, some sort of initialisation or boot-up routine may be required to ensure correct behaviour. This may also be the case following other events such as an interrupt or reset.
A known way of providing a processor hardware boot-up sequence is to have a state machine within the processor that forces micro code down the core pipeline to achieve the desired initialisation effects. A drawback of this is the need to provide the state machine and store the micro code. Furthermore, the instructions or micro code need to be loaded into the pipeline and progress down it to be executed which takes time and adds a delay to the processor being ready. Additionally, the values stored at start up in instruction registers within the pipeline will be clocked through the pipeline ahead of the loaded code. Thus, there is the additional task of ensuring that they do not generate any undesired operations.